Ok a bit of background information is required here, patrol boats, even the Armidales, are combatants. They are "minor" warfare vessels, i.e. while frigates and destroyers are "majors".
All the OPV designs the RAN are looking at have combat systems and a larger gun than 25mm is required. These ships will be for all intents and purposes, as capable as the originally proposed OCVs because the OCV concept was nothing more than a sexed up OPV with the save (or less) capability than OPVs being acquired by other navies around the world.
Back on the gun, the larger calibre will most likely be a 35 or 40mm and most likely turreted, but a RWS is still a possibility, as is a 57mm though probably the least likely option. Like I said, they will be combatants, not because this is a new requirement, but because that's what the RANs PBs have always been, the OPVs will just be bigger, more durable, longer ranged and more flexible, i.e. better able to do the job the CoA has tasked them.